Solomon Islands regional geochemistry

Two geochemical surveys were undertaken in the Solomon Islands between 1976 and 1983 as part of a combined geological mapping and mineral exploration project. The survey of Choiseul and the Shortland Islands was carried out between 1976 and 1979 by the Institute of Geological Sciences (now the British Geological Survey) with support from staff of the Geology Division of the Ministry of Land, Energy and Natural Resources, Solomon Islands. The project produced 12 geological maps at 1:50,000 scale as well as a series of unpublished reports. The survey of the New Georgia Group of islands was undertaken between 1979 and 1983. The project produced 7 geological maps at a scale of 1:100,000 and a regional map of the entire island group at a scale of 1:250,000. A series of multielement geochemical anomaly maps were produced at a scale of 1:100,000 to accompany each of the published geological maps. Master copies of these are held at the Geological Survey in Honiara. Full descriptions of the methods used are described in the margins of the anomaly maps. A total of 8848 stream sediment samples were collected from Choiseul and 7441 from the New Georgia Group, resulting in an average sampling density for the two areas of 2.68 samples per km2 and 1.47 samples per km2 respectively. Sampling in the Shortland Islands was confined to the larger islands, 187 were collected from the Fauro Island group, 148 from Alu and 69 from Mono. The samples were dry sieved and the fraction passing -80 mesh B.S. (177 microns) was analysed. A hot concentrated nitric acid digestion was used prior to analysis by atomic absorbtion spectrophotometry (AAS) for Co, Cu, Pb, Zn, Ni, Ag, and Mn. Samples from the vicinity of the Siruka Ultramafic Complex were determined for Cr by AAS after digestion by a bisulphate fusion technique. Raw data can be obtained from the Geology Division, Ministry of Mines and Energy, PO Box G37, Honiara, Solomon Islands.